High-pressure processing before freezing and frozen storage of European hake (Merluccius merluccius): effect on mechanical properties and visual appearance

High-pressure processing (HPP) is a non-thermal technique of growing interest for fish preservation. In this work, the effect on physical properties of European hake (Merluccius merluccius) caused by HPP, followed by freezing and frozen storage at −10 °C for 5 months, was evaluated in an accelerated frozen storage study. Following a central composite design, five pressure levels (range 150–450 MPa) and frozen storage time (range 0–5 months) were tested. Colour parameters (L*, a* and b*), expressible water and texture parameters were evaluated on raw and cooked muscles. Results showed that a low-pressure level (150 MPa) allowed adequate expressible water for raw muscle up to 2.5 months of frozen storage time. Values of 150 or 169.27 MPa did not cause significant changes on L* values of raw muscle. Overall, HPP led to changes on texture parameters of fresh muscle before and after cooking. However, 300 MPa and 5 months of frozen storage showed adhesiveness values for raw muscle alike that of non-treated fresh muscle. Moreover, 150–300 MPa for 5 months of frozen storage resulted in cohesiveness and chewiness values for cooked muscle like cooked fresh hake, showing that the HPP improves the quality of frozen hake.